The question is in the title, really. I have seen this distinction being made since March this year in regards to COVID-19 strategies, but how long have epidemiologists used this categorization? Is it in any classic textbooks? Has suppression been tried without vaccine before?

Here the distinction is made in the influential Imperial College report by Ferguson et al, from March 16, 2020.

Whilst our understanding of infectious diseases and their prevention is now very different compared to in 1918, most of the countries across the world face the same challenge today with COVID-19, a virus with comparable lethality to H1N1 influenza in 1918. Two fundamental strategies are possible2:

(a) Suppression. Here the aim is to reduce the reproduction number (the average number of secondary cases each case generates), R, to below 1 and hence to reduce case numbers to low levels or (as for SARS or Ebola) eliminate human-to-human transmission. The main challenge of this approach is that NPIs (and drugs, if available) need to be maintained – at least intermittently - for as long as the virus is circulating in the human population, or until a vaccine becomes available. In the case of COVID-19, it will be at least a 12-18 months before a vaccine is available3. Furthermore, there is no guarantee that initial vaccines will have high efficacy.

(b) Mitigation. Here the aim is to use NPIs (and vaccines or drugs, if available) not to interrupt transmission completely, but to reduce the health impact of an epidemic, akin to the strategy adopted by some US cities in 1918, and by the world more generally in the 1957, 1968 and 2009 influenza pandemics. In the 2009 pandemic, for instance, early supplies of vaccine were targeted at individuals with pre-existing medical conditions which put them at risk of more severe disease4. In this scenario, population immunity builds up through the epidemic, leading to an eventual rapid decline in case numbers and transmission dropping to low levels.

The strategies differ in whether they aim to reduce the reproduction number, R, to below 1 (suppression) – and thus cause case numbers to decline – or to merely slow spread by reducing R, but not to below 1.

  • What distinction? We require questions here to demonstrate some degree of prior research, so the obvious thing for this question to include would be a link to an explanation of this distinction. Adding that would greatly improve your question.
    – Carey Gregory
    Commented Oct 11, 2020 at 4:05
  • 1
    Good point. I added a link. I’m wondering if this was a novel categorization by Ferguson, or common knowledge among epidemiologists.
    – bgp2000
    Commented Oct 11, 2020 at 10:24
  • 3
    Just a friendly nod - Text provided in a screenshot is discouraged for various reasons. Please quote the text in text format at least so those using screen reader technologies can understand it. Commented Oct 11, 2020 at 14:11
  • Meh, it doesn't make much sense as a distinction if you read it carefully. I mean the last sentence in "mitigation" is talking about reducing cases, which could be distinct from reducing the transmission rate (R) but just before it talks of "population immunity builds up" which implies a lower R as fewer people are susceptible... Commented Dec 22, 2020 at 14:33
  • You can read the CDC epidemiology textbook in full here cdc.gov/csels/dsepd/ss1978/SS1978.pdf It doesn't mention "mitigation" or "suppression", although it does discuss the usual stuff, "herd immunity" etc. Commented Dec 22, 2020 at 14:37

1 Answer 1


From another 2020 paper which makes this distinction (in those terms) but cites an older 2020 paper that never mentions "suppression" but e.g. refers to China's strategy as "containment"... it's easy to search for the (right) terms in the 6th ed. of the Dictionary of Epidemiology, which again doesn't mention "suppression" but...

containment: The concept of regional eradication of a communicable disease, first proposed by Soper in 1949 for the elimination of smallpox. Containment of a worldwide communicable disease demands a globally coordinated effort, so that countries that have effected an interruption of transmission do not become reinfected following importation from neighboring endemic areas.

Mitigation is a less obscure term, but only defined rather broadly in that dictionary as

mitigation: Reduction of the risk of disaster. Actions taken to avoid or minimize negative environmental, medical, or social impacts

The [re]definition in sharper terms of R is pretty new, I conclude, and in line with the UK government's focus on R (at the time anyway), which has itself received some flak.

One could argue that "containment" is a somewhat bad term for "regional eradication", and that "suppression" is a better one, but I haven't quite seen someone make this word argument explicit.

A March 2020 OECD paper, while making the same rough dichotomy uses "containment":

In the absence of effective drugs and vaccines, containment and mitigation measures are the key public health interventions currently available to minimise the dramatic health consequences caused by COVID‑19. More specifically:

Containment strategies aim to minimise the risk of transmission from infected to non-infected individuals in order to stop the outbreak. This may include actions to detect cases early on and trace an infected individual’s contacts, or the confinement of affected persons;

Mitigation strategies aim to slow the disease, and to reduce the peak in health care demand. This may include policy actions such as social distancing, including a full society ‘lock-down’, and improved personal and environmental hygiene.

It's not too clear who wrote that, as they only give some OECD secretariat contacts, and they might not be the actual authors...

As far putting containment in opposition to mitigation... it's hard to say when such a contrast started to be made. A quick search finds at least one 2015 paper from China on their response to the 2009 H1N1 outbreak that speaks of containment and mitigation, and looking a bit through the paper I don't see a place where they make a sharp contraposition. So it may be a bit hard to find when the distinction was turned into a clear contrast.

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